Extrusion press



July 17, 1934. D 1,966,953

EXTRUSI'ON PRESS Filed June 20, 193:5 s Sheets-Sheet 1 INVENTOR ayw L4 ATTORNEYS I Ju ly 17, 1934. A. LIEIIBERGELD 1,966,953

EXTRUS I ON PRES S Filed June 20, 1935 3 Sheets-Sheet 3 14 "fly;

ATTORNFY-S Patented July 17, 1934 UNITED STATES PATENTOFFl-CE" EXTRUSION PRESS Alfred Liebergeld, Nuremberg, Germany, assignor,

by mesne assignments,

Switzerland to Tubus A. G., Zurich,

Application June 2.0, 1933, Serial No. 676,617 In Germany August-4, 1931 14 Claims.

heated' billet.

A further objectof my invention is to provide a mechanism comprising a mandrel and a punch for extruding the -billet that have greater ranges of movement than the length of the stroke of a crank arm for actuating them to ,pierce the billet and to extrude it around the mandrel.

In the operation of extruding billets to form seamless tubes by means of a mechanical press having a crank arm that 'moves at relatively high speed, it has been necessary to provide a press of, relatively large measurements in order to provide the necessary range of movement of the operating parts and to provide sufiicient mechanical strength to resist the stresses to which the parts are subjected when the billet is extruded at a relatively high rate. Such weights and dimensions of the press have been necessary because of the range of movement that has been required for the crank arm and because of the stresses that have been caused by the operation or the crank arm through a path of movement having a relatively long radius to exert the necessary force upon the billet. v

In accordance with the present invention, I am able to reduce the length of the crank arm, that is, the radius of the path of movement thereof, whereby it is possible to'reduce the weights and the dimensions of certain of the operating parts, while producing the same effects with respect to the billets to be extruded as have been produced by the mechanisms of the prior art. I

In accordance with the present invention, I provide a mandrel-carrier for piercing the billets and a hollow punch which serves as a guiding means for themandreland also as means for pressing the billet to extrudeit through the usual die around the mandrel to produce a seamless tube. .The mandrel carrier and the punch carrier, as well as a piston for actuating the mandrel carrier, arearranged in telescoping relation and each is relatively movable with respect to the other.

In order to provide a greater range of movement for the mandrel and the punch and accordingly of their respective carriers, I provide the mandrel-carrier in the form of a cylinder :which surrounds the piston that is in turn connectedto the crank arm of the mechanical press. The cylinder may be actuated to place the mandrel in position to pierce the billet by hydraulic means for supplying liquid to the cylinder which causes it to move relative to the piston. Means are thus provided for fixing the relative positions of the cylinder and the piston when the mandrel is in position to pierce the billet. Accordingly. when the crank arm operates to actuate the piston through its cycle the cylinder is actuated through a corresponding cycle thereby and the cylinder has a path of movement that is longer than the stroke of the crank arm by the amount of displacement between the piston .and the, end of the cylinder that is caused by'the liquid supplied thereto or by any other suitable means.

The punch and the mandrel and their respective carriers are retained in posit-ions most remote from the billet container by any suitable means such, for example, as a hydraulic cylinder or suitable mechanical means connected to the crank operating mechanism. This retaining 8 means, which when operated, permits the mandrel carrier and the punch carrier to move to positions in which the mandrel" and thepunch engage the end of the billet, also returns these parts to their initial positions after they have performed their respective functions of piercing and extruding the billet.

truded; Fig. 2 is a similar view in which the mandrel and the punch have been advanced to positions closely adjacent to the end of the billet; Fig. 3 isa similar view illustrating the po-- sitions of the'severalparts at approximately the completion of the extruding operation, Fig. 4

is a view similar to Figfyl of a. modified form of my invention; Fig. 5 s a view similar to-Fi'g. 3 illustrating the mandfeland punch in engagement with a billet; Fig. 6 is a View similar to Fig. 4 illustrating the various parts in their respective positions corresponding to the com pletion of the extrusion of a billet.

Referring particularly to Figs. 1, 2 and 3, an extrusion press constructed in accordance with my invention comprises a main-frame 1 within the lower part of which is mounted a press table 2 on which are mounted a matrix die 3, through which billets are extruded, and a billet container 4. Y

The operating mechanism for extruding billets comprises a crank shaft 5, a crank arm 6 and a crank pin? which actuates a connecting rod 8 that is secured by means of a ball and socket joint 9 to a reciprocable piston 10. The piston 10 is mounted in a cylinder 12 at the lower end of which is secured a mandrel support 13 having at its outer end a piercing mandrel 14. The cylinder 12 which is mounted for vertical movement relative to the piston 10 thus constitutes a mandrel carrier that is actuated by the piston 10 under conditions that will be later described.

Surrounding the cylinder 12 and mounted in vertical guideways 15 is a member 16 that carries at its lower, end a hollow punch 1'? that constitutes guiding means for the mandrel 14 and the mandrel support 13 and also operates to extrude a billet from the billet container 4. The punch carrier 16 is provided at its upper end with an inwardly extending flange 18 that is adapted to engage an outwardly extending flange 19 on the lower end of the cylinder 12 in order to limit the downward movementof the member 16 relative to the cylinder 12.

The punch carrier 16 is provided with a lateral projection 21 that is connected to the piston rod 22 of a piston 23 that operates in a hydraulic cylinder 25 having pipes 26 and 2'7 connected thereto for the admission of high pressure liquid and low pressure liquid, respectively. The cylinder 25 and the piston 23 control the vertical positions of the punch carrier 16 and the mandrel carrier or cylinder 12 in that they retain these parts in their upper positions or permit them to be actuated to lower positions in which the mandrel and the punch are adjacent to the end of the billet.

' The relative positions of the piston 10 and the cylinder 12 are controlled by hydraulic apparatus comprising a pipe 29 for supplying liquid under pressure through a valve 30 and a port 31 to the interior of the cylinder 12'. A safety valve 32 is connected to the pipe 29 between the valve 30 and the port 31 by means of two telescoping pipes 33 and 34. A pipe 35 constitutes 'an outlet for liquid under pressure when the spring 36 of the safety valve 32 has been sufliciently compressed to permit liquid to flow therethrough. c

In the operation of the form of my invention described above, it may be assumed that the various parts are in the respective positions in which they are illustrated in Fig. 1 and that a highly heated steel billet 38, having a temperature, for example, of 1200 to 1300" C., has been placed in thebillet container 4. When the mandrel carrier and punch carrier are in their fully retracted positions in which they are shown in Fig. 1, they are retained therein by the piston 23 and the rod 22, since high pressure water is admitted to the cylinder 25 through a valve 39 and the pipe 27. Low pressure water is constantly supplied to the pipe 26 at the upper end of the cylinder butthe piston 23 remains in its upper position by reason of the difference in pressures applied thereto.

The valve 39 is operated to cut off the supply of high pressure water and to permit the water on the lower side of the piston 23 to exhaust through a pipe 40. At the same time the valve 30 is opened to admit water through the pipe 29 and port 31 into the cylinder 12 below the piston 10. The valve 30 is connected to a source of water under pressure for quickly supplying a relatively large quantity.

The operation of the hydraulic apparatus referred to above permits the punch carrier 16 to drop vertically by gravity and the cylinder 12 to move downwardly until these parts have the relative positions shown in Fig. 2 in which the punch 17 and the mandrel 14 are adjacent the upper end of the billet 3B. The valve 30 is then' closed to lock the cylinder 12 in its extended position relative to the piston 10 and the crank shaft 5 and crank arm 6 are placed in operation.

The crank shaft 5 is connected to driving means of great power for moving the crank arm 6 and the parts connected thereto at relatlvely high speed. The shaft 5 rotates. in a clockwise direction as viewed in Figs. 1, 2 and 3. to cause the piston 10 to first actuate the cylinder 12 to cause the mandrel 14 to pierce the billet and when the cylinder 12 engages the punch carrier 16 it causes the punch 17 to extrude the billet 38 at relatively high speed through the matrix die 3 and around the mandrel 14 to form a seamless tube.

The operation of extruding the billet occurs at a speed of the punch 17 which may be, for example, from four to five inches per second. This rate of movement is sufficient to causethe billet to be extruded into a seamless tube about forty feet in length during a total period of less than two seconds. The effect of the operation of extruding the billet at such high speed is to effect the entire operation before the billet has cooled sufiiciently to oflerthe high resistance that would otherwise be present if the temperature of the billet had decreased materially before the extruding operation was completed.

The crank shaft 5 is stopped when it has completed a revolution and again occupies the position in which it is illustrated in Figs. 1 and 2. The piston 10, cylinder 12and punch carrier 16 will also be returned by the piston 10 to corresponding positions. To return the cylinder 12 and the punch carrier 16 to their fully retracted positions in which they are. illustrated in Fig. 1, the valves 30 and 39 are opened, the former permitting water to escape from the cylinder 12, and the latter admitting hgh pressure water to the lower end of the cylinder 25, and the 'piston 23 is raised to lift' the punch carrier 16 and the cylinder 12 engaged thereby to the positions in which-they are shown in Fig. 1 and in which they will be retained so long as the valve 39 is open.

Upon the completion of the cycle of operation referred to above the extruded seamless tube 42, Fig. 3, is removed in a well-known manner and the matrix die 3 andv the billet container 4 are prepared for the succeeding operation which will be similarin all respects to that described above- While the operationof the hydraulic means for spacing the lower end of the cylinder and the piston 10 has been limited to a movement of the cylinder 12 that will cause the lower end of the mandrel to be adjacent to the upper end of the billet, it will be appreciated that the piercing of the billet may be accomplished prior to the operation of the crank 6. Ifthe length of the cylinder 12 is increased to permit the cylinder 12 to move downwardly relative to the piston ,10 to such distance as to pierce the billet, such modification is, of course, within the scope and spirit of my invention.

Reference may now be had to Figs. 4, 5 and 6 in which are illustrated a modified form of invention in which mechanical means are substltuted for the hydraulic means of the abovedescribed form of my invention for controlling the positions of the cylinder 12 and punch carrier 16 relative to the piston 10 and to each other, In the latter form of my invention, many of the parts are identical with those of the preferred form and are identified by similar reference numerals.

' The crank shaft 5 is provided with a cam 43- which coacts with a roller 44 of a pivoted lever 45. The lever 45 is connected by a link 46 to the outer-end of a pivoted lever 47, the inner end of which is bifurcated to constitute a yoke 48 and the ends of which yoke are pivotally connected to relatively short links or push rods 49 that are in turn pivotally connected to the punch carrier 16.

As in the previous form of my invention, the space between the lower end of the piston 10 and the lower end of the cylinder 12 is controlled by hydraulic means. The cylinder 12 is connected by a pipe 50 to a valve 51 having a chamber 52 which communicates with'the safety valve 32 by means of telescoping pipes 33 and 34. The valve 51 is provided with a partition wall 53 which separates the chamber 52 from a second chamber 54. The partition wall 53 is provided with a central orifice 55 that is adapted to be closed by a valve disc 56 when the latter is held over the opening by means of a spring 57 which surrounds a valve stem 58connected to the valve disc 56.

The outer end of the valve stem 58 is provided with a roller 59 which coacts with a stationary cam 60 to control the opening through the partition wall of the valve 51. The cam 60 is mounted on a bracket 61 secured to the press frame. The valve chamber 54 is connected by means of a pipe 62 to a reservoir, not shown, of water to be quickly supplied to the cylinder 12 as will be later described.

In the operation of this form of my invention it may be assumed that the parts occupy the positions in which theyv are shown in Fig. 4 and that a billet 38 has been placed in the billet container 4. The crank shaft 5 and the cam 43 connected thereto are rotated in a clockwise direction, as viewed in the drawings. The roller 44 slides over a curved portion 63 of the cam 43 to permit the punch carrier 16 and the cylinder 12 to drop by gravity, the valve 51 being open to permit water to flow into the cylinder 12.

This arrangement causes the punch'carrier 16 and the mandrel carrier 12 to move downwardly faster than the piston 10 which is actuated by crank shaft 5 and crank arm 6. The shape of the cam 43 is preferably such that the punch carrier 16 and mandrel carrier 12 are permitted to occupy their most remote positions from the piston 10 after the crank arm has passed an angle of 20 to 30 from its vertical position. In these remote positions of the punch carrier and mandrel carrier, the lower ends of the mandrel l4 and the punch 17 are closely adjacent to the upper end of the billet.

While the mandrel carrier 12 is advancing, water is being supplied through the open valve 51 to the lower portion of the mandrel carrier until the lower end of the latteris sufliciently spaced from the piston 10. When the parts are in approximately the positions illustrated in Fig. 5 the cylinder 12 and the connected pipe 50 and valve 51 have moved downwardly and the roller 59 has moved to the tapered end of the stationary cam 60, thus permitting the valve disc 56 to close the orifice 55 in the valve 51 to prevent escape of the liquid in the lower portion of the cylinder 12 when the force of the piston 10 is applied thereto during the later portion of the crank stroke. The liquid constitutes a solid connection between the piston 10 and the cylinder 12 and the mandrel 14 is actuated to pierce the billet.

When the cylinder 12 engages the punch carrier 16 the punch 1'? is actuated to extrude the billet in the manner previously described in connection with the above-described form of extrusion press. tion, the roller 44 is out of engagement with the cam 43 and accordingly the link and lever mechanism is permitted to follow the movement of the punch carrier 16 to which it is positively connected.

After the crank arm thus has passed its lowermost vertical or dead center position, the piston 10 and the cylinder 12 begin their back stroke while the punch carrier 16 remains in its lowermost position during the early portion of the back stroke of the crank. When the cooperating flanges on the lower portion of thecylinder 12 and the upper portion of the punch carrier 16 arein engagement, the punch carrier 16.

moves upwardly with the other vertically moving parts. The positions of the various parts, when the flanges are in engagement, are illustrated in Fig. 6. Approximately one-half of the back stroke of the crank has been completed.

The roller 44 of the lever 45 again engages the cam '43 during the latter portion of the back stroke of the crank arm 6 and the link and lever mechanism connected thereto operate to return the punch carrier 16 and the cylinder 12 to the positions shown in Fig. 4, the upwardly moving valve 51 having in the meantime been opened by the cam 60 to permit the escape of liquid through the pipe 50.

The provision of hydraulic means for controlling the relative positions of the piston connected to the crank arm and the cylinder which constitutes the mandrel carrier enables the press to have a working stroke that is materially longer than the crank stroke of the press. This arrangement permits the crank arm to be materially shorter and thus decreases the length of the lever arm that is required to pierce the billet and to extrude the latter in the operation of forming the seamless tube.

The shorter lever arm or crank arm permits a corresponding decrease in the force that is required to operate the press and to correspondingly diminish the weight and dimensions of the parts thereof. The resultant saving in space and the diminished requirements with respect to material for the press, together with the reduction in power required, have resulted in material economies in the construction and operation of presses of the character of my invention.

I claim:

1. A press for extruding seamless tubes from solid. billets comprising a crank arm, a piston connected to said crank arm, a cylinder surl? rounding said piston and axially movable relative thereto, a mandrel carried by said cylinder, a member telescoping with said cylinder, a hollow'punch carried by said member for guiding said mandrel, and means for causing said cylinder and said member to move into positions in which said mandrel and said punch are in engagement with a billet to be extruded and for supplying said cylinder with liquid to fix the position of the piston therein when the latter is mandrel to pierce said billet and said punch to extrude said billet around said mandrel.

2. A press for extruding seamless tubes from solid billets comprising three telescoping members that are relatively movable, one of said members being adapted to actuate the others, a second of said members carrying a mandrel, a third of said members carrying a punch for pressing a billet to be extruded, auxiliary driving means for advancing the mandrel carrier and the punch carrier to their most 'advanced positions and for returning them to their fully retracted positions, main driving means for actuating said one member to actuate the other members and thereby cause the mandrel to pierce said billet and' the punch to extrude the 'E'iillet around said mandrel, and means forflxing the relative positions of said one and said second members for actuation of the latter bythe former member.

3. A press for extruding seamless tubes from solid billets comprising three telescoping members that are relatively movable, one of said members being adapted to actuate the others, a second member carrying a mandrel, a third member carrying a punch for pressing a billet to be extruded, auxiliary driving means for advancing the mandrel carrier and the punch carrier to their most advanced positions and for main driving means for actuating said one member to actuate the other members and thereby cause the mandrel to pierce said billet and the punch to extrude the billet around said mandrel and hydraulic means for fixing the relative positions of said one and said second members for actuation of the latter by the former member.

4. A press for extruding seamless tubes from solid billets and comprising a stationary matrix die, a mandrel carrier having connected thereto a mandrel for piercing a billet to be extruded, a punch carrier having connected thereto a hollow punch for guiding the mandrel and for extruding the pierced billet, auxiliary driving means for simultaneously effecting the movement of said mandrel carrier and said punch carrier to place the mandrel and the punch in position adjacent the billet and for returning them into their initial positions, and main drives ing means for actuating said mandrel carrier to place said billet and for actuating said punch lto cause said billet to be extruded around said lmandrel. I

\ 5. A press for extruding seamless tubesf'i'rom solid billets comprising three telescoping/memf' rs that are relatively movable, one of ,said members being adaptedto actuate the others, a second member carrying a mandrel, a} third member carrying a punch for pressing a billet be extruded, auxiliary driving means for adactuated by said crank arm for causing said returning them to their fully retracted positions,

vancing said second and third members into their most extended positions and for returning them into their fully retracted positions, main driving means for actuating said one member to actuate the other members to thereby cause the mandrel to pierce said billet and the punch to extrude the billet around said mandrel, said main driving meansbeing independent of said auxiliary driving means, ,and means for fixing the relative positions. of" said one and second members for actuation of the latter by the former.

6. A press for extruding seamless tubes from solid billets comprising three telescoping members that are relatively movable, one of said members beingadapted to actuate the others, a second member carrying a mandrel, a third member carrying a' punch for pressing a billet to be extruded, auxiliary driving means for advancing said second and third members into their most extended positions and for returning them into their fully retracted positions, main driving means for actuating said one member to actuate the other members and thereby cause the mandrel to pierce said billet and the punch to extrude the billet around said mandrel, said main driving means being adapted to operate and control said auxiliary driving means, and means for fixing the relative positions of said one and second members for actuation of the latter by the former.

'l. A press for extruding seamless tubes from solid billets comprising a crank arm, a piston connected to said crank arm, a cylinder surrounding said piston and axially movable thereto, a. mandrel carried by said cylinder, a member telescoping with said cylinder, a hollow punch carried by said member for guiding said mandrel, means coacting with said member for causing said cylinder and said member to move into positions in which said mandrel and said punch are in engagement with a billet to be extruded and for returning them into their fully retracted positions, and means for supplying said cylinder with liquid to fix the position or the piston therein when the latter is actuated .by said .crank arm for causing said mandrel to pierce said billet and said punch to extrude said billet around said mandrel.

8. A press for extruding seamless tubes from solid billets comprising a rotatable crank arm having a limited throw, a piston connected thereto and reciprocated thereby, a mandrel carrier adapted to beengaged by said piston and having a mandrel connected thereto, a punch for extruding the billet around the mandrel and movable relative to said piston, the punch carrier being adapted. to be engaged by saidmandrel carrier, and means for moving said mandrel carrier and said punch into'advanced positions relative to said piston and for locking the mandrel carrier in such position with a positive connection to the piston whereby movement of the latter by said crank arm actuates the mandrel to pierce the billet and the punch to extrude the billet around the mandrel.

9. A press for extruding seamless tubes, comprising three telescoping merfnbers that are relatively movable, one of said ,dnembers' being adapted to actuate the others a second or said members carrying a mandrel, a third of said members carrying a punch for pressing abillet to be extruded, auxiliary driving means for advancing the mandrel carrier and the punch carri er-into advancedpositionsrelative to the bil- L1.

let and for returning them to their fully retracted positions, main driving means actuating said one member to actuate the other members and thereby cause the mandrel to pass through said billet and the punch to extrude the billet around said mandrel, and means for fixing the relative positions of said one and said second members for actuation of the latter by the former member.

10. A press for extruding seamless tubes, comprising three telescoping members that are relatively movable, none of said members being adapted to actuate the others, a second member carrying a mandrel, a third member carrying a punch for pressing a billet to be extruded, auxiliary means for advancing the mandrel carrier and the punch carrier into advanced positions relative to the'billet and for returning them to their fully retracted positions, main driving means for actuation of; said one member to actuate the other members and thereby cause the mandrel to pass through said billet and the punch to extrude said billet around said mandrel, and hydraulic means for fixing the relative positions of said one and said second members for actuation of the latter by the former member.

11. A press for extruding seamless tubes, comprising a frame, a punch carrier movable in the frame, a. punch having a longitudinal bore connected to said punch carrier, a hollow mandrel carrier movable within the punch carrier and provided with a mandrel movable through the punch bore, a piston movable within said mandrel carrier, auxiliary driving means acting on said punch carrier for advancing the punch and mandrel substantially into contact with a billet to be extruded and for retracting said carriers after extrusion,'and main driving means associated with said piston for advancing the punch and mandrel to efiect extrusion of the billet around said mandrel.

12. A press for extruding seamless tubes, comprising a-frame, a punch carrier movable in the frame, a punch having a longitudinal bore connected to said punch carrier, a hollow mandrel carrier provided with a mandrel movable through the punch bore, a piston movable within said punch carrier, auxiliary driving means acting on said mandrel carrier for advancing the punchand mandrel substantially into contact 'with a billet to be extruded and for retracting said carriers after extrusion, main driving means associated with said piston for advancing the punch and mandrel to efiect piercing of the billet and extrusion around said mandrel, and means associated with said mandrel drel carrier, hydraulic means acting on said punch carrier for advancing the punch and mandrel substantially into contact with a billet to be extruded and for retracting said carriers after extrusion, main driving means separate from said hydraulic means associated with said piston for advancing the punch and mandrel to eflect piercing and extrusion around said mandrel, and a second'hydraulic means acting to fix the position of said piston in said mandrel carrier under the action of said main drivingmeans.

14. A press for extruding seamless tubes,'comprising a frame, a punch carrier movable in the frame, a punch having a longitudinal bore connected to said punch carrier, a hollow mandrel carrier movable within the punch carrier and provided with a mandrel movable through the punch bore, a piston movable within said mandrel carrier, hydraulic means acting on said punch carrier for advancing the punch and mandrel substantially into contact with a billet to be extruded and for retracting said carriers after extrusion, a second hydraulic means supplying fluid between said piston and mandrel carrier to fix their relative positions during extrusion, and main crank driving means connected to said piston for advancing the punch and mandrel to effect extrusion around said mandrel.

. ALFRED IEBERGEID.

Patent No. 1,966, 953.

ALFRED LIEBERGELD.

July 17, 1934.

it is hereby certified our error w s the printed mama. of the above numbered patentrequiring correction as follows: Page 5, line 49, claim 12, for, ."punch" 'readmandrel; and line 76, same claim, for "mandrel" read punch and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office. 4 Signed and sealed this 11th day of September, A. D. 1934.

(Seal) Leslie Frazer Acting Commissioner of Patents let and for returning them to their fully retracted positions, main driving means actuating said one member to actuate the other members and thereby cause the mandrel to pass through said billet and the punch to extrude the billet around said mandrel, and means for fixing the relative positions of said one and said second members for actuation of the latter by the former member.

10. A press for extruding seamless tubes, comprising three telescoping members that are relatively movable, none of said members being adapted to actuate the others, a second member carrying a mandrel, a third member carrying a punch for pressing a billet to be extruded, auxiliary means for advancing the mandrel carrier and the punch carrier into advanced positions relative to the'billet and for returning them to their fully retracted positions, main driving means for actuation of; said one member to actuate the other members and thereby cause the mandrel to pass through said billet and the punch to extrude said billet around said mandrel, and hydraulic means for fixing the relative positions of said one and said second members for actuation of the latter by the former member.

11. A press for extruding seamless tubes, comprising a frame, a punch carrier movable in the frame, a. punch having a longitudinal bore connected to said punch carrier, a hollow mandrel carrier movable within the punch carrier and provided with a mandrel movable through the punch bore, a piston movable within said mandrel carrier, auxiliary driving means acting on said punch carrier for advancing the punch and mandrel substantially into contact with a billet to be extruded and for retracting said carriers after extrusion,'and main driving means associated with said piston for advancing the punch and mandrel to efiect extrusion of the billet around said mandrel.

12. A press for extruding seamless tubes, comprising a-frame, a punch carrier movable in the frame, a punch having a longitudinal bore connected to said punch carrier, a hollow mandrel carrier provided with a mandrel movable through the punch bore, a piston movable within said punch carrier, auxiliary driving means CERTIFICATE Patent No. 1,966,953. I I I ALFRED acting on said mandrel carrier for advancing the punchand mandrel substantially into contact 'with a billet to be extruded and for retracting said carriers after extrusion, main driving means associated with said piston for advancing the punch and mandrel to efiect piercing of the billet and extrusion around said mandrel, and means associated with said mandrel carrier and punch carrier. limiting their relative movement.

13. A press for extruding seamless tubes, comprising a frame, a punch carrier movable in the frame, a punch having a longitudinal bore connected to said punch carrier, a hollow mandrel carrier movable within the punch carrier and provided with a mandrel movable through the punch bore, a piston movable within said mandrel carrier, hydraulic means acting on said punch carrier for advancing the punch and mandrel substantially into contact with a billet to be extruded and for retracting said carriers after extrusion, main driving means separate from said hydraulic means associated with said piston for advancing the punch and mandrel to eflect piercing and extrusion around said mandrel, and a second'hydraulic means acting to fix the position of said piston in said mandrel carrier under the action of said main drivingmeans.

14. A press for extruding seamless tubes,'comprising a frame, a punch carrier movable in the frame, a punch having a longitudinal bore connected to said punch carrier, a hollow mandrel carrier movable within the punch carrier and provided with a mandrel movable through the punch bore, a piston movable within said mandrel carrier, hydraulic means acting on said punch carrier for advancing the punch and mandrel substantially into contact with a billet to be extruded and for retracting said carriersafter extrusion, a second hydraulic means supplying fluid between said piston and mandrel carrier to fix their relative positions during extrusion, and main crank driving means connected to said piston for advancing the punch and mandrel to effect extrusion around said mandrel.

. ALFRED LIEBERGELD.

or CORRECTION.

I I July 17. 1934.

LIEBERGELD.

it is hereby certified that error appears in the printed .snec'LfiI iltiQli 0f the above numbered patent 12, for, "much" read.

requiring correction as follows: Page 5, line 49, claim mandrel; and line 76, same claim, for "mandrel" read punch and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office. 4 Signed and sealed this 11th day of September, A. D. 1934.

(Seal) Leslie Frazer Acting Commissioner of Patents 

